The Plastic Tarp: No-Till Weed Control for the Smart and Lazy

Thrillseekers,

Tarps at sunset

Tarped sections of the farm

One ideal that I brought with me to farming was the idea of no-till. No-till is a big practice from the permaculture community and is seen frequently on large-scale permaculture farms. Many smaller scale or urban farms have yet to adopt this practice. Tilling is still seen as the best way to prepare beds and control weeds from season to season.

The principle behind no-till is the idea that tilling disrupts the delicate balance of microorganisms that feed the plants you grow as well as stimulates weeds in your beds. By not tilling, fewer weeds are exposed to the surface to germinate, which reduces the weed pressure. If you are interested in hearing more about the symbiotic relationship of plants and microorganisms, I encourage you to do some research into Dr. Elaine Ingham’s work.

Some will argue that productivity is enhanced by no-till systems. I think in most urban farming settings, you likely won’t see a dramatic difference in actual crop productivity with tilling versus no-tilling. Even if you till extensively and completely wreck the microorganism balance, chances are you are using compost or other organic matter additives that add those back into the soil. I have not tested this myself, but it is my speculation. If anyone has trials that they have done for high rotation crops, I’d be happy to hear it.

Weeds can be nasty things and organic farmers struggle with them to seemingly no end. On a farm where you are harvesting baby vegetables, the last thing you want to do is sift through a field of weeds to find your crops. Weeds develop anywhere there is a niche in the soil system that needs to be filled. This means weeds appear in your rows and in between sparsely planted crops. This is one reason why urban farming advocates planting very densely. No light on the ground means no weeds.

Weeds serve a purpose in the system, so stop getting angry at them and figure out what purpose they serve. If you can fill that with something else, weeds won’t appear. There are a couple purposes for weeds, but a key driver for their appearance is exposed ground. The ground does not like to be exposed. Between the sun and erosion, exposed dirt can have a rough time. A weed covering shades the ground from the sun allowing moisture to be held closer to the surface and promoting healthier soil organisms. It also dampens rainfall and holds soil together to prevent precious top soil from being washed away. If you can find a way to cover the ground, weeds won’t need to protect the ground.

You will always have weeds. Sorry, can’t avoid it. But what you can do is reduce them. Combining no-till practices with strategic killing of weed seeds will over time reduce weed pressure. A removable black tarp is a key tool for accomplishing this. A UV-stabilized tarp can be laid out on top of beds and aisles in between plantings to cause weeds to germinate and die. I got the idea of using tarps from Jean Martin Fortier’s book The Market Gardener and started using them from the beginning and have found them to be invaluable. The trick is being persistent about putting them back after a crop is done or you have an unplanted bed. Weeds quickly regrow, and I have been bitten several times by not doing this.

Tarped ground

Ground underneath tarp over winter.

One downside to using a tarp that I have been particularly frustrated with is that the brand I have been using occasionally slips in a non-UV-stabilized tarp. If you think plastic takes thousands of years to decompose, leave some out in the sun for a couple months and see what happens. If it hasn’t been UV treated, it will likely shatter into an incomprehensible number of tiny pieces. This is what happened with one tarp that I had out on the ground. It was a complete mess to clean up, and there will forever likely be plastic out in the field. I thought it was a one-time occurrence, but I had a second tarp from them do the same. I would say it is time to start looking for a different vendor, but they are a pretty high profile name already.

I guarantee you will feel ridiculous for the amount of money you will pay for large pieces of plastic that you lay on dirt, but the money is well worth it in weeding and crop loss costs. There are several more techniques for successfully applying no-till practices on your farm. They shall soon follow.

Tarp Dos

  • Use a tarp!
  • Watch for signs of sun damage. If it looks like the tarp isn’t UV-stabilized, get it OUT IMMEDIATELY. Watch for chunks breaking off easily or feeling brittle.
  • Be persistent about replacing tarps. It’s worth the extra couple of minutes.

Until next time,

The Failing Farmer

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